TEXT OF THE DESCRIPTION

Field of invention

The present invention refers to safety valves for domestic water systems and has been developed with particular attention being paid to overpressure valves, intended for use in combination with storage water heaters, such as household water heaters and the like.

State of the art

Household electric water heaters, and more generally storage water heaters for sanitary applications, are normally equipped with a safety valve, mounted between the water inlet of the water heater and the water supply network.

An example of such a valve is shown schematically in Figure 18. The valve, indicated as a whole with 100, has a hollow body 101 with an inlet IN and an outlet OUT, and is provided with a flow control insert, designated as a whole with 102, as well as a safety valve arrangement, designated as a whole with 103. The control insert 102 - which basically operates as a unidirectional or non-return valve - is configured to enable passage of water from the water mains (inlet IN) to the water heater (outlet OUT), in the direction indicated by the arrow F, when a pressure drop occurs inside the water heater (for example in the order of 0.1 -0.2 bar), and at the same time prevent a reverse flow, that is, from the water heater to the water mains.

On the other hand, the safety valve arrangement 103 - which basically operates as an over-pressure valve - is designed to avoid an excessive increase in pressure inside the water heater: therefore, upon reaching a pressure considered potentially dangerous, the safety arrangement 103 automatically determines the outflow of hot water from the water heater, through a corresponding drain opening 103a , and interrupts this outflow when the safety pressure conditions have been restored. The aforementioned drain opening 103 a has often an additional hose associated thereto, in order to convey the drained water to a desired point, and thus avoid its dispersion in the installation environment of the water heater.

In safety valves of the type indicated, the body 101 is generally formed of metal material, defining two generally tubular portions connected in fluid communication and often arranged substantially transversely with respect to each other, typically in a substantially T-shaped configuration. A first portion 101a, in which the flow control insert 102 is housed, is open at both the opposite ends and substantially obtains the duct for water inlet from the water mains to the water heater. The second portion 101b, i.e., the portion that houses the safety valve arrangement 103 and that defines the aforementioned drain opening 103 a, has one end 101b' in fluid communication with the first portion 101a, at an intermediate point between the respective inlet IN and outlet OUT, and is closed at the other end, e.g., by means of a sealing disk, possibly with at least one associated gasket.

In certain circumstances, it may be necessary to drain water from the water heater, for example when its heating element has to be replaced, or when the risk of freezing of the contents of the water heater has to be avoided (typically in the case of mountain dwellings). In some solutions, therefore, in order to allow this "controlled" drain operation without having to disconnect the pipes that connect the water heater between the water mains and the water-sanitary system, the safety valve arrangement 103 includes a control lever 103b. This control lever 103b - which is associated with a shaft of the safety valve arrangement 103 passing through a respective hole of the aforementioned sealing disk - is operable to manually cause the opening of the valve arrangement, and thereby cause the outflow of water through the aforementioned drain opening 103 of the valve itself.

Examples of safety valves for water heaters of the type indicated above are described, for example, in the Italian patent IT 1293399 B of the same Applicant.

As explained above, in safety valves of the type indicated - such as the one exemplified - the flow control insert 102 is inserted into the first tubular portion 101a of the valve body 101, intended for connection between the water mains and the water heater. The structure of the insert 102 essentially includes a positioning and supporting member, for example a plastic element defining a plurality of peripheral passages aimed at allowing the passage of water, as well as a central hole in which a portion of the end of a stem 102a or similar guiding element is able to slide. At the opposite end of this stem an ON/OFF valve member is associated, comprising a sealing plate 102b made of resilient material, typically a polymer, which is intended to operate in closure at a valve seat VS obtained by an intermediate narrowing of the duct defined by the first tubular portion 101a of the body 101.

Between the above-mentioned positioning and supporting member and the above-mentioned ON/OF valve member there is set at least one calibrated spring 102c, which surrounds a corresponding part of the stem 102a and which pushes the valve member including the plate 102b into the closed position of the valve seat VS. In the mounted condition of the safety valve 100, in case of pressure drops inside the water heater, as already indicated above, the pressure of the water present in the water mains overcomes the elastic reaction of the spring 102c and allows the valve member, i.e., the plate 102b thereof, and the stem to recede, thus allowing passage of water through the valve seat VS and the peripheral passages of the aforementioned positioning and supporting member, in order to reach the inside of the water heater. Otherwise, the action of the spring 102c and the water pressure present in the water heater urges the valve member in its respective closed position, which prevents the backflow of water from the water heater to the water mains.

The Applicant found that, in unpredictable circumstances that may occur in the hydraulic circuit formed by the water mains and the water heater, for example in the case of a back-pressure Pl from the water mains with a value equal or close to 0, and therefore a pressure lower than the pressure P2 existing inside the water heater, water leaks may be generated between the sealing plate 102b and the valve seat VS. The concept is exemplified in figure 19, wherein the dotted lines highlight the possible leakage of water towards the outlet OUT of the valve.

In practice, under such conditions, the elastic reaction force of the spring 102c is not sufficient to ensure that the water pressure from the water heater prevents possible leakage between the plate 102b and the valve seat VS. This is due to the fact that, given the function of the spring 102c, its reaction force cannot exceed a relatively modest value: if this force were greater, in fact, in case of low pressure in the water mains, the water would not be able to reach the water heater (for this reason, the spring 102c is generally calibrated to allow a passage of water to the water heater even at pressures below 1 bar).

This problem occurs, for example, in certain geographical areas where - for example in the summer months - there are more or less prolonged interruptions in the water supply. The consequence is that, during these interruptions, and as a result of the aforementioned leaks, the water content of the water heater is progressively lost to the water mains.

Summary and aim of the invention

In view of the above, the present invention essentially aims to obtain a safety valve of the type indicated that allows to cope even with the aforementioned unpredictable circumstances that may occur in the hydraulic circuit, i.e., to prevent the aforementioned possible leakage of water from the outlet to the inlet of the valve. An auxiliary aim of the present invention is to obtain one such valve in which the problem is solved in a simple and economical way. This and other aims are achieved, according to the present invention, by a safety valve for water heaters, in particular a valve against overpressures, having the characteristics referred to in the attached claims. The claims form an integral part of the technical teaching provided herein in connection with the invention.

Brief description of the drawings

Further aims, characteristics and advantages of the present invention will be clear from the detailed description that follows, made with reference to the attached drawings, provided purely as an explanatory and non-exhaustive example, wherein:

- Figures 1, 2 and 3 are schematic views, respectively in perspective, in lateral elevation and in frontal elevation, of a safety valve according to possible embodiments of the invention;

- Figure 4 is a schematic section according to line IV-IV of Figure 3;

- Figure 5 is a partial and schematic section of a valve body of Figure 4;

- Figures 6 and 7 are schematic views, respectively in perspective and lateral elevation, of a safety valve flow control insert according to possible embodiments of the invention;

- Figure 8 is a schematic section according to line VIII- VIII of Figure 7;

- Figures 9, 10 and 11 are schematic views, respectively in perspective, in lateral elevation and in frontal elevation, of a sealing element of a safety valve according to possible embodiments of the invention;

- Figure 12 is a schematic section according to line XII-XII of Figure 11;

- Figure 13 is a larger scale view of detail XIII of Figure 4;

- Figures 14, 15, 16 and 17 are views similarly to those of Figures 9, 10, 11 and 12, respectively, relating to a variant embodiment;

- Figure 18 is a schematic section, similar to that of Figure 4, of a safety valve of a known type;

- Figure 19 is a larger scale view of detail XIX of Figure 18; and

- Figure 20 is a schematic section similar to those of Figures 12 and 17, of a sealing element of a safety valve according to further possible embodiments of the invention.

Description of embodiments of the invention The reference to "an embodiment" in this description indicates that a particular configuration, structure, or characteristic described in relation to the embodiment is included in at least one embodiment. Thus, phrases such as "in one embodiment", "in various embodiments" and the like, possibly present in different places of this description, do not necessarily refer to the same embodiment, but may instead refer to different embodiments. Moreover, particular conformations, structures or characteristics as defined within this description can be combined in any appropriate way in one or more embodiments, even different from those depicted. The numerical and spatial references (such as "upper", "lower", "high", "low", etc.) refer to the examples in the figures and used here only for convenience and therefore do not limit the scope of the embodiments. The same reference numbers are used in the figures to indicate similar or technically equivalent elements.

Referring initially to figures 1-5, 1 designates as a whole a safety valve for a water heater according to possible embodiments of the invention: assume below that valve 1 is intended for connection between a water supply network and an electric storage water heater.

The valve 1 has a valve body 2 formed of a metal material, for example brass, but obtaining the valve body 2 at least partly with plastic material is not excluded from the scope of the invention. In the exemplified valve body 2 there are identifiable a first tubular portion 3 and a second tubular portion 4, the portion 4 being preferably arranged transversely with respect to the portion 3. In the nonlimiting example shown, the portion 4 is arranged substantially orthogonal to the portion 3, with a generally “T”-shaped configuration of the valve body 2, but in other embodiments the portion 4 can extend with a certain inclination with respect to the portion 3, or it can also extend substantially parallel to the portion 3.

The first portion 3 defines a duct - designated by MC only in figure 5 - which has an inlet end 3IN and an outlet end 3QUT, opposite to each other and intended for connection with the water mains and an inlet of the water heater, respectively. The terms "inlet end" and "outlet end" are used here in consideration of the flow direction under normal operation of the water heater, i.e., when the water is fed from the water mains to the inside of the water heater. To this end, in Figures 1, 2, 4 and 5, the arrow F indicates the direction normally followed by the flow of water from the water mains to the water heater, i.e., from the inlet end 3 IN to the outlet end 3QUT of the duct. In various embodiments, a first area of the body 2 at the inlet end 3IN is prearranged for connection to the water mains, while a second area of the body 2 at the outlet end 3OUT is prearranged for connection to the water heater. Referring in particular to Figures 4 and 5, in various preferential embodiments, the aforementioned first area - designated by 3a - is at least partly substantially maleshaped, i.e., designed to receive on its exterior a corresponding part of a hydraulic connection or joint connected to the water mains: for this purpose, preferably, the prearrangement of the area 3a comprises a male thread defined on the outside of the valve body 2. In various preferential embodiments, the aforementioned second area - designated by 3b - is at least partly substantially female-shaped, that is, it is designed to receive inside it a corresponding male part of a hydraulic connection or joint belong to the water heater, or connected thereto: for this purpose, preferably, the prearrangement of the area 3a comprises a female thread defined inside the valve body 2, i.e., of the duct MC. Of course, in possible variant embodiments, the connection arrangement of the two areas 3a and 3b could vary from what is shown in the drawings, depending on the types of hydraulic connections or fittings provided on the side of the water mains and on the side of the water heater, respectively.

Referring again to Figures 4 and 5, the tubular portions 3 and 4 of the valve body 2 communicate with each other by means of an opening or passageway, designated by 5, which is located in an intermediate position with respect to the inlet end 3IN and outlet end 3OUT.

As also explained in the introductory part of this description, inside the duct MC of the tubular portion 3 a flow control assembly or insert is housed, designated as a whole with 6 in Figure 4, which operates essentially as a unidirectional or non-retum valve. Inside the duct SC (Figure 5) defined by the tubular portion 4 there is instead a safety valve arrangement, designated as a whole with 7 in Figure 4, which operates essentially as an automatic over-pressure valve.

The arrangement 7 may be made in any known manner. In various preferential embodiments, the arrangement 7 essentially comprises an ON/OFF valve member 8 configured for cooperating in a sealing relation with respect to a valve seat 9, preferably defined at the passageway 5. The ON/OFF valve member 8, for example made of rubber or the like, is associated with an end of a shaft or stem 10, which passes through a corresponding central opening (not indicated) of a disk or plate 11, which closes the tubular portion 4 at the upper end thereof, and to which a suitable gasket may possibly be associated. In the example shown, the arrangement 7 also comprises an adjustment ring 12, which can be screwed into a female thread defined in the upper region of the tubular portion 4, this ring 12 also performing a positioning function for the upper end of a helical spring 13; the valve member 8 preferably defines or has associated thereto an element 14 for the positioning of the lower end of the spring 12. In an intermediate position at the two ends thereof, the tubular portion 4 has a drain opening 4a. In various embodiments, such as the one exemplified in the drawings, the upper end portion of the stem 10 protrudes outside the tubular portion 4, beyond the closing disk 11, and has associated thereto a lever 16, for example via a pin 15. As explained in the introductory part of this description, the function of the lever 16 is to allow, if need be, the manual opening of the valve arrangement 7, to discharge the contents of the water heater through the outlet end 3QUT and the drain 4a, which communicate with each other through the passageway 5.

In use of the valve 1, when the pressure on the side of the water heater (i.e., at the outlet end 3QUT) exceeds a threshold value determined by the load of the spring 13 (for example 8 bar), the valve member 8 and the stem 10 may rise relative to the valve seat 9, causing compression of the same spring, thereby opening the passageway 5 to allow water to flow from the water heater from the drain opening 4a; in this phase - and as it will be see - the water pressure present on the side of the water heater keeps an ON/OFF valve member (22, 23) of the insert 6 in a closed position, so preventing the outflow of the same water towards the water mains (i.e., towards the inlet end 3 IN).

The flow control insert 6 can also be made in any known manner, except for the particular construction of a sealing element (22) thereof, which is the main aspect of the present invention.

In various preferential embodiments, and referring to Figures 4 and 6-8, the flow control insert 6 comprises a positioning and supporting member 20, for example made of plastic material. The member 20 has a central opening 20a (Figure 6), through which a guiding element or stem 21 is slidingly inserted, at the proximal end of which a widened head 21a is defined, to which the aforementioned sealing element 22 according to the invention is associated. In various embodiments, the sealing element 22 has a generally annular disc- or plate-shape. The element 22 is preferably formed with an elastically deformable material, such as an elastomer, in order to perform its sealing functions with respect to a corresponding valve seat SV. The head 21a of the guiding element 21 and the sealing element 22 have respective mutually facing surfaces. As it can be seen, the guiding element 21 and the sealing element 22 are configured as separate (distinct) parts.

In various embodiments, the positioning and supporting member 20 also defines a series of peripheral passages 20b for the passage of water. In various embodiments, such as the one exemplified in the figures, the positioning and supporting member 20 of the insert 6 is in the form of a disk, having the aforementioned central opening 20a for the guiding element 21 (hereinafter identified as "stem", for simplicity) and a series of peripheral openings that define the passages 20b. In other embodiments, the member 20 may instead include a central plate, provided with the opening for stem 21, from which a series of spokes or similar elements extend in a radial direction.

In various embodiments, the sealing element 22 can define or have associated thereto at least one element 23 for the positioning of the first end of a helical spring 24, such as a disc or plate element with a central hole for the stem 21. The aforementioned spring 24 surrounds a corresponding part of the stem 21 and its second end abuts against the member 20. In these embodiments, the elements 22 and 23 may be considered as part of an ON/OFF valve member of the insert 6. In various embodiments, such as the one shown, the sealing element 22 and the positioning element 23 are configured as separate (distinct) parts.

The spring 24 is calibrated so that its reaction force does not exceed the force determined by the nominal pressure of the mains water, or has a maximum reaction force such that the water can anyway reach the water heater; in various embodiments, the spring 24 is calibrated for allowing passage of water to the water heater even at pressures below 1 bar.

In various embodiments, such as that represented, there can be provided an additional helical spring, such as the one designated by 25, extending between the valve member (here between the element 23 associated with the sealing element 22) and a corresponding abutment surface 21b formed or associated in an intermediate area of the stem 21. The function of this second possible spring 25 is to enable a substantially controlled spilling of water towards the inlet end 3IN, i.e., towards the water mains, in presence of a modest over-pressure (for example 1.5 bar) on the side of the water heater, i.e., an over-pressure of a lower entity than that which causes the opening of the safety valve arrangement 7.

For example, heating of water inside a water heater causes a small increase in the volume of the water itself, which causes the aforementioned modest overpressure. In case of absence of water withdrawal from the water heater - for a relatively prolonged time (for example a weekend) - it is preferable for safety reasons to eliminate the persistence of the aforementioned modest over-pressure: the presence of the spring 25, properly calibrated, then allows a certain recession of the stem 21 with respect to the sealing element 22, due to the thrust caused by the modest over-pressure.

As mentioned, the element 23 has a central hole, in which a corresponding first portion of the stem 21- indicated by 211 in Figure 8 - passes through. Preferably, this hole in the element 23 is sized or shaped such that that at least one first passageway is defined between the hole itself and the outer surface of the portion of the stem 211. In the example shown in Figure 8, such a first passageway is designated by 23a. Similarly, the sealing element 22 has a hole or central passage (22a ¹ , Figure 9), through which a corresponding second portion of the stem - indicated by 2h in Figure 8 - passes through. Again, the shape and/or perimeter dimensions of the hole of the sealing element 22 can be chosen so as to define a second passageway, designated by 23b in Figure 8, with respect to the corresponding portion of the stem 2h: in the example, for this purpose, the diameter of the central hole of the sealing element 22 is slightly larger than the stem portion 212, to define the passageway 23b.

In this way the water - passing through the passageways 23a and 23b - can reach the side of the head 21a of the stem 21 facing the outlet 3QUT and, in the presence of the aforementioned overpressure from the water heater, cause a modest recession of the stem 21 against the action of the spring 25, for example a recession of about 1.5 mm. In this phase, the sealing element 22 is in any case kept against a valve seat VS, also by means of the spring 24 (see for example Figure 4), such that the backward movement of the stem 21 causes a slight separation between the head 21a and the sealing element 22, with a consequent passage of water towards the inlet 3 IN, through the abovementioned passageways 23a and 23b of the elements 23 and 22, respectively. After this overpressure has been removed by tapping water to the water mains, the action of the calibrated spring 25 brings the stem 21 back to its original position, of closure between head 21a of the stem 21 and the corresponding face of the sealing element 22. The substantially determined threshold value that causes stem 21 to recede naturally depends on the calibration of spring 25.

The valve seat VS with respect to which the sealing element 22, visible in Figure 5, is intended to cooperate, is defined by an annular portion or wall 3c of the valve body 2 arranged transversely, i.e., protruding towards the inside of the duct MC, reducing the passage section thereof. The aforementioned annular wall 3c has an inner end portion that comprises an annular protrusion or relief 3d generally directed towards the outlet end 3QUT of the duct MC. The external profile of the relief 3c preferentially has a generally tapered conformation, in particular a substantially truncated conical conformation. As it can be seen, for example in Figure 13, the sealing element 22 is intended to rest on top of the relief 3d.

In various embodiments, such as the one exemplified, the wall 3c defining the valve seat VS is defined in a recessed position with respect to the end of the valve body 2 that defines the inlet 3IN, that is, in an area of the duct MC (Figure 5) that is intermediate to the inlet 3IN and the outlet 3QUT. By the way, in other embodiments, the wall 3c may be at the aforementioned end of valve body 2 which defines the inlet 3IN.

The positioning and supporting device 20 of the insert 6 is positioned inside the duct MC defined by the tubular portion 3, preferably upstream with respect to the area or thread 3b, and preferably also upstream with respect to the passageway 5, having as a reference the direction of the water flow indicated by the arrow F, and the sealing element 22 is in turn upstream of the passageway 5, between the positioning and supporting member 20 and the valve seat VS.

Inside the duct MC delimited by the tubular portion 3, a suitable positioning and fixing area is defined the for element 20, upstream of the area or thread 3b, always referring to the flow direction F, particularly in a substantially cylindrical section of the duct MC. The aforementioned substantially cylindrical section, indicated by MCi only in Figure 5, preferably has an internal diameter smaller than the internal diameter of the cylindrical section of the duct MC indicated by MC2, wherein the female zone or thread 3b is defined. In preferred embodiments, the positioning and fixing area for the member 20 is defined by a specific seat, designated by 31 in Figures 4 and 5, which is very preferably a seat with a female thread. For these embodiments, the member 20 preferably has a circular external profile 20c (Figures 6-8) and is provided with a male thread suitable for engagement with that of the seat 31. In other embodiments, the member 20 can be formed with a deformable material, that is, with its outer profile 20c such that it stably mates within the seat 1, when pressed into it; within this frame, the seat 31 could be a coupling seat even free of a thread. The insert 6 is pre-assembled and then inserted into the duct MC of the tubular portion 3, starting from the end 3OUT, until the member 20 reaches the cylindrical section MCi downstream of the passageway 5, where it is fixed in position at the seat 31. In the mounted condition, the sealing element 22 is abuts against the valve seat VS, and is pushed into this position due to the action of the spring 24.

For the purpose of the mounting safety valve 1 in the working position, its body 2 is coupled to a connection or joint of the water heater, with a male part of this connection or joint being received in the area 3a of the duct MC, acting as a female connecting part. On the other hand, the inlet end 3IN of the tubular portion 3 is instead connected to the water mains, for example by means of a flexible pipe, equipped with a suitable connection or joint with a "female" part, for example having a female thread that is screwed onto the area 3a equipped with a complementary thread.

When valve 1 is used, if inside the water heater (i.e., at the outlet end 3QUT) a pressure drop occurs (for example in the order of 0.1 to 0.2 bar), the pressure of the water from the mains (i.e., at the inlet end 3 IN) is such that the elastic reaction of the spring 24 is overcome, thereby allowing the sealing element 22 and then the stem 21 to slide, so as to open the valve seat VS. When the pressure between the ends 3IN and 3QUT subsequently returns to equilibrium, the action of the spring 24 re-closes the sealing element 22 on the valve seat VS. It will also be appreciated that, in the aforementioned equilibrium condition, or in the event of a pressure drop on the side of the water mains, the insert 6 enables to prevent a flow of water from the water heater to the water mains.

If, on the other hand, inside the water heater (i.e., at the outlet end 3QUT) a modest overpressure occurs (that is, having a value smaller than the intervention pressure of the safety arrangement 7), the pressure of the water that creeps from the water heater into the passageways 23a, 23b (Figures 4 and 8) is such as to overcome the elastic reaction of the spring 25, thus allowing a slight recession of the stem 21, and thus the separation of the head 21a thereof from the sealing element 22, with a consequent passage of water to the water mains. When, subsequently, the pressure between the ends 3 OUT and 3IN returns to equilibrium, the action of the spring 25 causes the head 21a of the stem 21 to close against the sealing element 22.

As indicated above with reference to the known technique exemplified in Figures 18 and 19, under unpredictable pressure conditions between the water mains and the water heater, water leakage may occur between the sealing plate 102b and the valve seat VS, since the spring 102c of the insert 102 may not have the force necessary to prevent such a leakage. For example, suppose that - for any reason - there is no water pressure at inlet end 3 IN and that, conversely, the water contained in the water heater, and therefore downstream of the sealing element 22, is at a lower pressure (for example 2 bar) than the intervention pressure of the safety arrangement 7 and of the "controlled tapping" arrangement managed by the spring 25; under these conditions, the aforementioned undesired leakage of water towards the water mains occurs.

According to the invention, the sealing element 22 has, at a face thereof facing the inlet end 3 IN of the duct MC, an annular sealing portion, which is configured to surround the relief 3d of the annular portion or wall 3c that defines the valve seat VS, and for elastically resting on the outside of this relief 3d, when the valve member 22, 23 is in its closed position of the valve seat VS, as determined by the spring 24.

An example of embodiment of the aforementioned annular sealing portion is visible in Figures 9-12 (as well as in Figures 6-8), where it is designated as whole with 22b. In the example, this annular sealing portion 22b comprises a generally protruding annular sealing lip, in particular a substantially truncated cone sealing lip.

In various embodiments, such as that shown in Figures 9 to 12, the sealing element 22 has a main body portion 22a, having a generally disc- or annular plateshape, with the annular sealing lip 22b protruding from a face 22a" of said main portion 22a, that is, the face which, in the assembled condition of the valve, is intended to be facing the inlet end 3IN of the duct MC. In the example, the main portion 22a has a hole or central passage 22a', through which a corresponding portion of the stem 21 (i.e., the portion previously indicated by 2h in Figure 8) is passing through.

As mentioned, in preferential embodiments, the annular relief 3d of the annular wall 3c defining the valve seat VS (Figure 5) has a generally tapered external profile, preferably a truncated cone one: for such cases, the sealing portion 22b has an internal sealing surface that is generally divergent starting from the aforementioned face 22a" of the main portion 22a (preferably a substantially truncated cone sealing surface), in order to receive the aforementioned relief £d.

As is noted, the sealing element 22 has no parts protruding inside the valve seat VS as delimited by the annular wall 3c.

The presence of the seal portion 22b allows to overcome the problems underlying the invention, as is can be deduced, for example, from the detail of Figure 13. When the valve member 22, 23 is in the closing position of the valve seat SV, the sealing element 22 abuts frontally on the valve seat SV, i.e., on the end of the annular relief 3d, in particular at a surface area of the face 22a" of the sealing element 22 which is circumscribed by the annular sealing portion 22b. In this position, the annular sealing portion 22b already surrounds the relief 3d and rests elastically thereon, in particularly on the outer side thereof. In other words, at the time of closure of the valve member 22, 23 as determined by the calibrated spring 24, two different sealing zones are obtained, through the face 22a" and the annular sealing portion 22b. In this way any, phenomena of water leakage can be avoided, thanks to the fact that the sealing portion or lip 22b is elastically pressed on the outside of the relief 3d, and the effect is then increased by virtue of the pressure of the water subsisting in the duct MC downstream of the sealing element 22, which has the effect of further urging elastically the portion or lip 22b on the outer side of the relief 3d; This last effect is further enhanced by the divergent shape of the sealing portion 22b.

In the case exemplified in Figures 9 to 12, the portion or seal 22b has a maximum outer circumference substantially corresponding to the maximum outer circumference of the main portion 22a of the sealing element 22. However, this is not an essential feature. For example, referring to the embodiment exemplified in Figures 14-17, the maximum circumference of the lip 22b is less than that of the main portion 22a of the sealing element 22. The choice may vary, for example, depending on the type and/or size of the valve (for example, the solution in Figures 9-12 may be used in the case of valves M18xl.5, while the solution in Figures 14- 17 may be used in the case of valves Gl/2").

However, the lip shape of the sealing portion 22b is not an essential feature. The aims of the invention can in fact be achieved with a configuration of the type shown in Figure 20, wherein the annular sealing portion 22b comprises a recess 22b' defined at the face 22a" of the portion 22a of the sealing element, where within the recess 22b' at least a part of the annular relief 3d defining the second valve seat VS is receivable. Even in embodiments of this type, the sealing element 22 is positioned abuts frontally on the valve seat SV, or on the end of the annular relief 3d, at a surface area of the face 22a" which identifies the bottom of the recess 22b'. Also in this case the sealing portion 22b rests elastically on the outside of the annular relief, and is then urged in this position by the pressure of the water downstream of the sealing element 22.

In preferential embodiments, the outer profile of the annular reliefs 3d and the inner sealing surface of the portion 22b have different taper angles. The best results were found to be obtained when the internal sealing surface of the portion 22b and the surface of the face 22a" form therebetween an external angle a (Figures 10, 15 and 20) of between 50° and 70°, preferably between 55° and 65°, most preferably approximately 60° (± 1 ). Preferably, this angle is lower (preferably of about 15°) than the homologous angle of the external surface of the annular relief 3d, in order to allow an elastic coupling of the sealing portion 22b on the relief 3d, even regardless of the stress exerted in this sense by the water downstream of the sealing element 22.

The main body part 22a of the sealing element 22 may be between 1 mm and 2 mm thick, preferably approximately 1,5 mm (± 0.1); the sealing portion may protrude from the face 22a" with a height of 0.5 to 1 mm, preferably approximately 0.8 mm (± 0.1). The sealing portion 22b, when shaped like a lip, can be between 0.2 and 0.4 mm thick. The outer diameter of the main portion 22a" can be between 11 and 16 mm, preferably between 12 and 15 mm, for example about 12 mm (± 1) or about 15 mm (± 1). The central passage 22a' of the portion 22a may have a diameter between 4 and 5 mm, preferably about 4.5 mm (± 0.1).

The body of sealing element 22 preferentially defines the portions 22a and 22b in a single piece and, as mentioned, is preferably formed of an elastomer material.

From the given description, the characteristics of the present invention are clear, as well as are its advantages. The safety valve described is essentially immune from the risks of unwanted water leakage at the valve seat SV, towards the supply network, as indicated in the introductory part. For this purpose, as explained, the sealing portion 22b is specifically designed to avoid these possible leaks towards the valve inlet, in conditions of substantial absence of water pressure at the inlet end 3IN of the valve, with the simultaneous presence of a higher pressure of the water contained in the water heater.

The sealing element 22 is simple and economical to produce, as it is a component which can be molded in large series.

It is clear that numerous variations are possible for the person skilled in the art to the safety valve described as an example, without departing from the scope of the invention as defined in the attached claims.

The stem 10 and the lever 16 are not essential elements of the safety valve arrangement 7 since - in possible alternative embodiments of the invention - these elements could be omitted. In this view, for example, the valve arrangement 7 of the valve 1 according to the invention could include only the elements 8 (and 14), 12 and 13, as shown in Figure 2 of IT 1293399 B; In this case, the closing disc 11 will not have any central passage.